The Back to the Future grad, who also won three Emmys for his role on Taxi, will guest star on the Dec. 1 episode of the comedy from Chuck Lorre, Bill Prady and showrunner Steve Molaro. Additional details about Lloyd’s role and the storyline are being kept under wraps.

“We’re so excited to be working with Christopher Lloyd, and think we’ve created a fun part that fans will really enjoy,” the executive producers said Wednesday in a joint statement.

Lloyd’s Big Bang Theory pit stop comes less than a month after he was tapped to guest star on Syfy’s time-travel drama 12 Monkeys.

The casting comes as Big Bang Theory still has some key family roles to fill for its ensemble, chief among them Howard’s (Simon Helberg) father’s. Speaking with THR ahead of season 10, Molaro said, “Howard’s father is something that’s always floating around the ether, but there are no plans at the moment.”

Lloyd joins an impressive list of guest stars to have popped in on Big Bang Theory, including fellow Taxialum Judd Hirsch, who played Leonard’s (Johnny Galecki) father.